In an ink jet printing apparatus using a plurality of printing heads arranged in a convey direction of a printing medium, an inclination angle of the printing medium to a predetermined convey direction is detected to adjust, in accordance with the resultant inclination angle, timings at which ink is jetted from the plurality of printing heads. This allows, even when the printing medium being subjected to a printing operation has a slight meander shape, an image to be formed on a printing medium so that printing positions of the plurality of printing heads have no dislocation.